<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .a{
            width: 300px;
            height: 500px;
            background-color: #a90f0f;
        }
        .b{
            width: 100px;
            height: 100px;
            background-color: #a9ea1b;
        }
        .c{
            width: 100px;
            height: 100px;
            background-color: #1150da;
            position: relative;
            top: 30px;
           left: 100px;
        }

    </style>
</head>
<body>
    <div class="a">
        <div class="b"></div>
        <div class="c"</div>
        
    </div>
</body>
</html>